Biotinidase deficiency is a disease caused by dysfunction of an enzyme called biotinidase. Patients having biotinidase deficiency experience severe clinical symptoms including irreversible neurological damage or even death. The gene defect for biotinidase deficiency is inherited and the disease typically emerges when two carriers pass it to their offspring. For each pregnancy of two such carriers, there is a 25% chance that the child will be born with the disease and a 50% chance the child will be a carrier for the gene defect. Studies show that approximately 1 of every 60,000 live births will have biotinidase deficiency. Infants with biotinidase deficiency appear normal at birth, but develop critical symptoms after the first weeks or months of life. With early diagnosis and treatment, all symptoms of this disease can be prevented.
In cells, biotinidase has the function of releasing biotin from biocytin and short biotinylated peptide chains for biotin recycling. Currently there are several available assays for measuring biotinidase activity in blood samples, although these assays are not always suited for clinical testing.
A method for measuring biotinidase activity using biotin coupled to fluorescent europium chelate has been disclosed (Curr. Trends Infant Screening 1989, 265). The cleavage of the amide bond between biotin and europium chelate resulted in a decrease in fluorescence intensity. Although the method might be suitable for quantitative homogenous measurement of biotinidase activity from serum, the method disclosed suffers from relatively high background signal and long incubation times.